As an example of procedures of manufacturing a semiconductor device such as a flash memory, a DRAM, and the like, a procedure of forming a film on a substrate is often carried out, where a cycle that non-simultaneously performs a process of supplying a precursor gas to a substrate and a process of activating a reaction gas, which differs in chemical structure from the precursor gas, and supplying the activated reaction gas to the substrate is performed a predetermined number of times.
However, depending on a process temperature during the film forming process, the activation of the reaction gas may be insufficient, which may deteriorate productivity of forming a film and lower the quality of the film. A method of activating a reaction gas with plasma may be employed, but the high energy of plasma in this method may damage a substrate.